The Drunken Lizard Pub

I was messing around with my armor and I noticed that when I took of my steel light armor, which weighs 10 lbs...my tohit went up by 5! I tried removing other pieces of armor but saw no effect.

my heaviest other piece of light armor is only six lbs.

what is the relationship of light armor wearing to your to hit ratio?

Just a guess, but could it be that there is not so much a direct relationship between your armour and your to-hit rating, but between encumberment and your to-hit rating?
Were you encumbered with the steel armour? I'm sure there are players here that would know more about these mechanics.

Think u r right I had a lot of loot from a dungeon

When you pick up an item in your inventory, whether it be in your backpack or on your body, the game temporarily subtracts the weight of the item from your total carried. If you were encumbered (which gives you ToHit penalties), picking up a piece of armor might have reduced your weight enought to remove the ToHit penalty (temporarily). Unless you actually toss the item, your ToHit goes back to were it was when you place the item back in your inventory.